package LC;

/**
 * https://leetcode.com/problems/sum-root-to-leaf-numbers/description/
 * Given a binary tree containing digits from 0-9 only, each root-to-leaf path could represent a number.
 * An example is the root-to-leaf path 1->2->3 which represents the number 123.
 * Find the total sum of all root-to-leaf numbers.
 * For example,
 * 1
 * / \
 * 2   3
 * The root-to-leaf path 1->2 represents the number 12.
 * The root-to-leaf path 1->3 represents the number 13.
 * Return the sum = 12 + 13 = 25.
 */
public class LC_129_SumRoottoLeafNumbers_Recur_BinaryTree {
    public static void main(String[] args) {
        TreeNode root = new TreeNode(1);
        root.left = new TreeNode(2);
        root.right = new TreeNode(3);
        root.left.left = new TreeNode(4);
        int sum = Solution.sumNumbers(root);
        System.out.println(sum);
    }

    static class TreeNode {
        int val;
        TreeNode left;
        TreeNode right;

        TreeNode(int x) {
            val = x;
        }
    }

    static class Solution {
        static int sumNumbers(TreeNode root) {
            return sumhelper(root, 0);
        }

        private static int sumhelper(TreeNode root, int levelBase) {
            if (root == null) return 0;
            if (root.left == null && root.right == null) return levelBase + root.val;
            int nextLevelBase = (levelBase + root.val) * 10;
            int leftSubTreeSum = sumhelper(root.left, nextLevelBase);
            int rightSubTreeSum = sumhelper(root.right, nextLevelBase);
            return leftSubTreeSum + rightSubTreeSum;
        }
    }
}
